1. Field of Invention
This invention relates to a method of forming an underfill layer on a bumped wafer. More particularly, the present invention is related to a method of forming an underfill layer on a bumped wafer, which further comprises the step of grinding wafer.
2. Related Art
In this information explosion age, integrated circuits products are used almost everywhere in our daily life. As fabricating technique continue to improve, electronic products having powerful functions, personalized performance and a higher degree of complexity are produced. Nowadays, most electronic products are relatively light and have a compact body. Hence, in semiconductor production, various types of high-density semiconductor packages have been developed. Flip chip is one of the most commonly used techniques for forming an integrated circuits package. Moreover, compared with a wire-bonding package or a tape automated bonding (TAB) package, a flip-chip package uses a shorter electrical path on average and has a better overall electrical performance. In a flip-chip package, the bonding pads on a chip and the contacts on a substrate are connected together through a plurality of bumps formed on the chip by a conventional bumping process and then an underfill material is filled into the gap between the chip and the substrate to encapsulate the bumps so as to well protect the bumps. In such a manner, the reliability of such flip chip package is enhanced.
As mentioned above, in a flip chip package, there is usually provided an underfill material between the substrate and the chip so as to enhance the reliability of the packaging products. In a conventional method, the underfill is dispensed at the peripheral of the chip or disposed through an opening of the substrate so as to be filled in the gap between the substrate and the chip. Hence, the bumps of the chip between the chip and the substrate are enclosed by the underfill material. However, this method usually spends a lot of time and causes a lot of voids in the underfill layer.
As disclosed in U.S. Publications 2002/0001688 and 2003/0034128, there is disclosed a wafer level packaging method. Therein, an underfill layer is preformed on a film and then the underfill layer with the film formed thereon is disposed on the bumped wafer and then a pressing and heating process is performed so as to have the underfill layer enclosing the bumps. Afterwards, the bumped wafer with the underfill layer formed thereon is singulated into a plurality of chips. However, the bumps are easy to be damaged when the underfill layer is pressing and heating. In addition, the film is not easy to be removed from the underfill layer. Besides, the process of grinding the backside of the wafer is not easy performed due to not enough protection for the bumps.
Therefore, providing another method to solve the mentioned-above disadvantages is the most important task in this invention.